Integrated thermistor and metallic element device and method

Abstract

A circuit protection device includes a fuse element placed in parallel with a PTC thermistor layer. The element and PTC thermistor layer are provided on one or more insulating substrate, such as an FR-4 or polyimide substrate. First and second conductors connect the fuse element and PTC thermistor layer electrically in parallel, such that current (i) initially under normal flows mainly through the fuse element and PTC thermistor layer at a lower drop in voltage and (ii) after an opening of the fuse element flows under normal operation through the PTC thermistor layer at a higher drop in voltage.

What is claimed is: 
     
       1. A circuit protection method comprising:
 protecting a first electrical pathway in a device using a substrate that comprises and operates as a resettable fusing apparatus having a first electrical resistance; and 
 protecting a second electrical pathway in the device that is electrically in parallel with the first electrical pathway with a non-resettable fusing apparatus extending along a surface of the substrate and having a second electrical resistance, wherein the first electrical resistance is relatively higher than the second electrical resistance such that current (i) initially under normal operation flows through both the resettable and non-settable fusing apparatuses at a lower drop in voltage, and (ii) after an opening of the non-resettable fusing apparatus flows under normal operation through the resettable fusing apparatus at a higher drop in voltage. 
 
     
     
       2. The circuit protection method of  claim 1 , wherein the resettable fusing apparatus includes at least one positive temperature coefficient layer. 
     
     
       3. The circuit protection method of  claim 1 , wherein the non-resettable fusing apparatus includes at least one fuse element. 
     
     
       4. The circuit protection method of  claim 1 , including configuring the device for operation in a tip or ring line of a telecommunications circuit. 
     
     
       5. The circuit protection method of  claim 1 , including configuring the device for operation in a voltage supply line between a data bus controller and a data bus connector. 
     
     
       6. The circuit protection method of  claim 1 , including configuring the device for operation in a charging line of a battery pack.